How does the weather impact your roasting proces ? I have written about it in this post http://coffeenavigated.net/changing-weather/. But this is complicated stuff – many things influence. It would be great to explore further.
So, I have started this project to collect data more systematic (pilot phase in June 2017). There might be a difference depending on the type of roaster. And in some climates the humidity varies more.
Would you like to join ? It will help you to know your conditions better.
NOTE: It requires that you often roast the same bean so you have a baseline on how it responds to your heat setting. This makes you able to tell when it behaves differently.
And it does take some effort to calculate the air water content from the relative humidity. And dedication to make registrations.
If so, write me on: email@example.com
I worked out a google sheet where all participants can fill in data. The challenge is to make a set-up that isn’t too complicated AND to exclude all the other factors that affect the roast. This will be refine here in June 2017 with the first participans (5 have already started).
Preparation: mapping your weather situation
To evaluate when you got an extreme weather condition that affects your roast … you have to gather a picture of your “normal weather” or medium … so you can state “Today has more humidity in the air” and so.
We need both temperature and humidity.
Regarding temperature you probably already have an idea. I live in Denmark. Most of the year the temperature is between 5°C and 15°C. So 20°C is higher than normal and 0°C is lower.
The humidity is measured with a Moisture Meter. But it will only give the relative humidity. The warmer it gets the more water the air can hold. So 90% humidity at 25°C has a lot more water than 90% at 5°C. As this graph shows:
So, to find what is extra high or low air water content where you live … you got to get both humidity and temperature data … and then calculate the water content by looking a the graph or using http://planetcalc.com/2167/
How to find humidity levels for your locations:
Find the official weather station near you – where you can get both data from the day and historical data. Both temperature and relative humidity (has to be measured at the time and at the same place).
You can also use your own instruments to log these data. But good calibration is needed. Moisture meters can easily measure 15% wrongly. Therefor data from an official weather is better. But if you live to far away, it wont represent the conditions where you are.
Select days through out the year that shows the variation where you live. Pick a low and high humidity day on cold winter days … and in spring/autumn … and in different kinds of warm summer days. Pick more days from warm summer days because the water content varies more at higher temperatures (if its 25 or 30 C)
If you have little variation through out the year, maybe 10 days is enough. Otherwiese use more.
Insert the data for these days in the google spread sheet and calculate the absolute humidity. You can use this one http://planetcalc.com/2167/
It also takes in Barometric pressure, but it doesn’t have a big influence when being at the same location. But if you are located 3000 meters above sealevel this important to calculate the water content.
I have made an area in the spread sheet for this.
When you got a good representation of how the weather varies at your location – then you can evaluate the limits; what is low water content where I live/what is high.
Maybee you start with one set of limits but then as you collect data on how it impacts your roast – then you adjust the limits.
Recording roast days
Makes notes both of days when the roasts behaves normal and when you suspect it to be affected by the weather – or when the weather is very different from normal. To get a full picture.
The impact on the roast relies on your evaluation compared with how the roast normally responds to the heat settings (the baseline).
Important: you should be aware if the first batch on the roaster needs more heat than the following – so this is eliminated from your evaluation of the weather impact.
The impact on the roast split up in to stages:
1) The start of the roast – how quickly do it get to yellowing point or First Crack ? Did the batch need more or less heat ?
2) Around First Crack start – here it’s normally nessecary to turn the heat down in advance to avoid to much rise in temperatur. Did you need to turn it more down than normal ? or less ?
To simplify things only note if you need more or less heat – or if it’s within normal range. In the comments you can note more details. Please do.
Then get weather data; outdoor temperature and relative humidity. Again calculate what that makes in Absolute humidity; grams water per cubic meter (m3).
Mark if the temperature and humidity is high than normal by coloring the value red.
Mark if the temperature and humidity is lower than normal by coloring the value red.
Leave it black if its in the normal range.